The present invention relates to a door lock, and more particularly to an actuator for an electronic door lock.
Electronic door locks typically include a mechanical lock and an electronic control for authorizing the use of the mechanical lock. A portion of the mechanical lock secures the door to the door frame. The electronic control may include, for example, a reader that permits data to be read from a coded medium such as a magnetic card, proximity card, or memory key. When a card or key with valid data is presented to the electronic control, the control permits an outer handle or door knob to operate a shaft of the mechanical lock by actuating a prime mover to either release a latch that was preventing the handle or knob from turning, or engage a clutch that couples a shaft of the handle or knob to the shaft of the mechanical lock.
The mechanical lock and electronic control components (including the prime mover and latch/clutch) of electronic door locks are commonly powered by alkaline batteries which typically have a service life of between about two to three years. This limited battery service life necessitates changing the batteries several times over the service life of the door lock; a process that increases the operating costs of businesses which employ the electrical locks. Many electronic locks utilize a piezoelectric bender as the prime mover to actuate the clutch or latch. Electronic door locks used in certain commercial and hospitality applications are commonly cycled between an office or free passage mode (used during the work day or peak traffic periods to permit entry through the door without the user first presenting a card or key to the reader), and a challenge mode which requires the user to present the card or key to the reader to gain entry through the door. To permit unchallenged entry through the door in the office mode, a conventional electronic door lock uses energy from the batteries to activate and maintain the engagement of the piezoelectric bender with the clutch. This energy drain reduces the service life of the batteries.